This application requests support to continue the investigators work in developing fetal magnetocardiography (FMCG) as a new noninvasive technology for obtaining functional information from the human fetus in utero. FMCG is the only technique that can assess fetal heart rate and rhythm with high precision, and thus could have a significant impact on perinatal science and clinical practice. The investigators previous finding to date suggest that the potential of FMCG is especially high for evaluation of fetal rhythm disorders. They have demonstrated several examples of fetal rhythm disturbances that could be detected by FMCG, but not by ultrasound. Importantly they were also able to infer the underlying mechanisms. FMCG is also a nearly ideal signal source for fetal hear rate monitoring, providing a precise signal, free of maternal interference, which can be detected throughout the last half of pregnancy. The investigators have shown that it can provide important diagnostic information, unobtainable by other means, which have the potential to improve the accuracy of fetal monitoring. The long-term goal of the research is to develop FMCG into a method that can improve clinical assessment of fetal cardiac function and fetal well being. The primary technical aims of the project are: 1. To make FMCG recordings over a wide range of gestational ages using newly acquired state-of-the-art instrumentation, and to evaluate the quality and success rate of the measurements; and 2. To apply specialized signal processing technology which can significantly increase the signal-to-noise ratio of FMCG recordings and thereby improve the resolution of smaller waveform components, which are essential for assessment of fetal rhythm. Building upon these advances, the primary scientific aims are: 3. To perform serial measurements in patients with a wide range of fetal rhythm abnormalities in order to demonstrate the efficacy of FMCG for investigating the mechanisms and development of serious fetal arrhythmia, and to document specific cases in which FMCG can provide an important diagnostic advantage over ultrasound; and 4. To record the FMCG at earlier gestational ages than previously possible, and to use these recording to assess fetal heart rate variability, fetal cardiac waveform parameters, and other potential indicators of fetal well-being in normal and high risk pregnancies.